Method for forming carbon-containing silicon/metal oxide or nitride film by ALD using silicon precursor and hydrocarbon precursor

ABSTRACT

An oxide or nitride film containing carbon and at least one of silicon and metal is formed by ALD conducting one or more process cycles, each process cycle including: feeding a first precursor in a pulse to adsorb the first precursor on a substrate; feeding a second precursor in a pulse to adsorb the second precursor on the substrate; and forming a monolayer constituting an oxide or nitride film containing carbon and at least one of silicon and metal on the substrate by undergoing ligand substitution reaction between first and second functional groups included in the first and second precursors adsorbed on the substrate. The ligand may be a halogen group, —NR 2 , or —OR.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 62/341,500, entitled “Method for Forming Carbon-Containing Silicon/Metal oxide or Nitride Film by ALD Using Silicon Precursor and Hydrocarbon Precursor,” and filed on May 25, 2016, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a method for forming a carbon-containing silicon/metal oxide or nitride film by atomic layer deposition (ALD) using a silicon/metal precursor and a hydrocarbon precursor.

Description of the Related Art

As a method for forming an amorphous film containing carbon, such as a SiC film, SiCN film, or the like, chemical vapor deposition (CVD) has been used for long time. However, when a plasma is used (i.e., plasma-enhanced CVD), surface reaction significantly occurs, lowering a step coverage. On the other hand, when heat is used (i.e., thermal CVD), extremely high process temperature is required, lowering practicability.

The present inventors have evaluated atomic layer deposition (ALD) for forming a carbon-containing amorphous film since ALD is known for good step coverage. However, in some cases, carbon contained in a precursor was not effectively adsorbed on a surface, especially on a sidewall of a trench pattern of a substrate, and thus, a film deposited on the sidewall became thin, lowering step coverage. The above problem became significant particularly when the size of the pattern was small. For example, when a carbon-containing amorphous film was deposited in a trench pattern having an opening of 70 nm and an aspect ratio of 2, the step coverage was approximately 90%, whereas when a carbon-containing amorphous film was deposited in a trench pattern having an opening of 30 nm and an aspect ratio of 3.5, the step coverage was drastically lowered to approximately 60%.

Thus, in a process which requires incorporation of SiC into a film, the adsorption of carbon tends to be low on a sidewall, and the step coverage on the sidewall tends to suffer. This problem occurred similarly for a film such as those constituted by SiCO, SiCN, or the like, although the step coverage of these films was better than that of a film constituted by SiC since these films contained nitrogen or oxygen as compared with the pure SiC film. That is, not only a SiC film, but also a SiCO film, SiCN film, or the like, had insufficient step coverage when being deposited in a small size trench pattern. The use of a plasma may contribute to the above problem since less plasma tends to reach a sidewall especially when a trench pattern is small. Based on the above experiment, the present inventors have worked on a new method to eliminate elements which interfere with adsorption of carbon on a sidewall.

Any discussion of problems and solutions in relation to the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.

SUMMARY OF THE INVENTION

In some embodiments, by using two different precursors having different ligands which easily cause ligand substitution reaction, at least one of the above-discussed problems can be resolved. In some embodiments, a precursor is divided into two precursors wherein a first precursor provides at least silicon or metal, and a second precursor provides carbon, and both the first and second precursors contain ligands which can effectively cause ligand substitution reaction. In some embodiments, a combination of ligands which can effectively cause ligand substitution reaction is a combination of a halogen group and —NR₂, a halogen group and —OR, a halogen group and halogen group, or —NR₂ and OR. The second precursor contains important components which determine film compositions. For example, the second precursor for forming an oxide film such as SiCO, SiOCN, or the like may require inclusion of a hydroxyl group as a ligand to form oxide, whereas the second precursor for forming a nitride film such as SiCN or the like may require inclusion of a C—N bond as a ligand to form nitride. The same approach can be taken for a metal oxide, metal nitride, or the like, where a metal, in place of silicon, constitutes a basic structure or primary skeleton of the first precursor. The ligand substitution reaction occurs at a certain temperature, and thus, thermal ALD can be employed for depositing a film; however, a plasma may be used in a situation where adsorption of a precursor needs to be improved, as in plasma-enhanced ALD. In this disclosure, SiC, SiCO, SiCN, SiCON, or the like is an abbreviation indicating a film type in a non-stoichiometric manner unless described otherwise.

For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Further aspects, features and advantages of this invention will become apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.

FIG. 1A is a schematic representation of a PEALD (plasma-enhanced atomic layer deposition) apparatus for depositing a protective film usable in an embodiment of the present invention.

FIG. 1B illustrates a schematic representation of a precursor supply system using a flow-pass system (FPS) usable in an embodiment of the present invention, wherein a precursor will be fed to a reactor in (a) and no precursor will be fed to the reactor in (b).

FIG. 2 illustrates a precursor supply system using an auto-pressure regulator (APR) according to an embodiment of the present invention, wherein a precursor will be fed to a reactor in (a) and no precursor will be fed to the reactor in (b).

FIG. 3 illustrates a precursor supply system using a bottle-out control system (BTO) according to an embodiment of the present invention, wherein a precursor will be fed to a reactor in (a) and no precursor will be fed to the reactor in (b).

FIG. 4 illustrates a precursor supply system using an APR with a BTO according to an embodiment of the present invention, wherein a precursor will be fed to a reactor in (a) and no precursor will be fed to the reactor in (b).

FIG. 5 shows a schematic process sequence of PEALD in one cycle according to a comparative example wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 6 shows a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 7 shows a schematic process sequence of PEALD in one cycle according to another embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 8 shows a schematic process sequence of thermal ALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 9 shows a schematic process sequence of thermal ALD in one cycle according to another embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 10 shows a schematic process sequence of PEALD in one cycle, followed by the schematic process sequence of PEALD illustrated in FIG. 6 or 7 according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process.

FIG. 11 shows a schematic process sequence according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In this disclosure, “gas” may include vaporized solid and/or liquid and may be constituted by a single gas or a mixture of gases. In this disclosure, a process gas introduced to a reaction chamber through a showerhead may be comprised of, consist essentially of, or consist of a precursor gas and an additive gas. The precursor gas and the additive gas are typically introduced as a mixed gas or separately to a reaction space. The precursor gas can be introduced with a carrier gas such as a noble gas. The additive gas may be comprised of, consist essentially of, or consist of a reactant gas and a dilution gas such as a noble gas. The reactant gas and the dilution gas may be introduced as a mixed gas or separately to the reaction space. A precursor may be comprised of two or more precursors, and a reactant gas may be comprised of two or more reactant gases. The precursor is a gas chemisorbed on a substrate and typically containing a metalloid or metal element which constitutes a main structure of a matrix of a dielectric film, and the reactant gas for deposition is a gas reacting with the precursor chemisorbed on a substrate when the gas is excited to fix an atomic layer or monolayer on the substrate. “Chemisorption” refers to chemical saturation adsorption. A gas other than the process gas, i.e., a gas introduced without passing through the showerhead, may be used for, e.g., sealing the reaction space, which includes a seal gas such as a noble gas. In some embodiments, “film” refers to a layer continuously extending in a direction perpendicular to a thickness direction substantially without pinholes to cover an entire target or concerned surface, or simply a layer covering a target or concerned surface. In some embodiments, “layer” refers to a structure having a certain thickness formed on a surface or a synonym of film or a non-film structure. A film or layer may be constituted by a discrete single film or layer having certain characteristics or multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers.

Further, in this disclosure, the article “a” or “an” refers to a species or a genus including multiple species unless specified otherwise. The terms “constituted by” and “having” refer independently to “typically or broadly comprising”, “comprising”, “consisting essentially of”, or “consisting of” in some embodiments. Also, in this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.

Additionally, in this disclosure, any two numbers of a variable can constitute a workable range of the variable as the workable range can be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments.

In the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. In all of the disclosed embodiments, any element used in an embodiment can be replaced with any elements equivalent thereto, including those explicitly, necessarily, or inherently disclosed herein, for the intended purposes. Further, the present invention can equally be applied to apparatuses and methods.

The embodiments will be explained with respect to preferred embodiments. However, the present invention is not limited to the preferred embodiments.

An embodiment of the present invention provides a method for forming an oxide or nitride film containing carbon and at least one of silicon and metal in a trench on a substrate placed in a reaction space by atomic layer deposition (ALD) conducting one or more process cycles, each process cycle comprising:

-   -   (i) feeding a first precursor in a pulse to the reaction space         to adsorb the first precursor on the substrate, said first         precursor containing at least one of silicon and metal, and a         first functional group selected from the group consisting of a         halogen group, —NR₂, and —OR, wherein each R independently         represents hydrogen or hydrocarbon group;     -   (ii) feeding a second precursor in a pulse to the reaction space         to adsorb the second precursor on the substrate, said second         precursor containing neither silicon nor metal, and a second         functional group selected from the group consisting of a halogen         group, —NR₂, and —OR, wherein each R independently represents         hydrogen or hydrocarbon group, wherein the first and second         functional groups are a combination of a halogen group and —NR₂,         a halogen group and —OR, a halogen group and halogen group, or         —NR₂ and —OR; and     -   (iii) forming a monolayer constituting an oxide or nitride film         containing carbon and at least one of silicon and metal on the         substrate by undergoing a substitution reaction between the         first and second functional groups of the first and second         precursors adsorbed on the substrate.

Accordingly, a carbon-containing film can successfully be formed with good conformality (e.g., more than 90%) even on sidewalls of a trench having an aspect ratio of more than 2, for example, by using the first and second precursors in combination, wherein the first precursor contains silicon (or metal) and at least one first ligand, and the second precursor contains no silicon (nor metal) and at least one second ligand, where the first ligand and the second ligand can undergo ligand substitution reaction.

Ligand substitution reaction can occur between —NR₂⇄—OR; hydrogen⇄hydrogen; hydrogen⇄—NR₂; and hydrogen⇄—OR, regardless of the main skeleton of the first and second precursors. For example, the following combinations of precursors can effectively undergo ligand substitution reaction:

TABLE 1 Combination of precursors Reactant Film Diiodosilane + Iodomethane H₂ plasma SiC Diiodosilane + Diiodomethane H₂ plasma SiC Disilabutane (H₃SiCH₂CH₂ SiH₃) + H₂ plasma SiC Diiodomethane Divinylmethylsilane + Diiodomethane H₂ plasma SiC Bisdiethyaminosilane + Ethyleneglycol O₂ plasma SiCO Triethylsilanol + glycerol H₂ gas SiCO Tris(t-pentoxy)silanol H₂ gas SiCO ((CH₂ (CH₃)₃CO)₃SiOH) + Ethyleneglycol Diiodosilane + Diethylamine H₂ gas/plasma; SiCN NH₃ gas/plasma Bisdimethylaminosilane + Diiodomethane H₂ gas/plasma; SiCN NH₃ gas/plasma

The functional groups contained in the first and second precursors may be referred to as “ligands” which undergo ligand substitution reaction. Either one of steps (i) and (ii) can start first; that is, the order of steps (i) and (ii) can be reversed.

The first precursor contains at least one of silicon and metal. The metal includes, but is not limited to, Zr, Ti, etc., wherein the first precursor includes, but is not limited to, trisdiethylamino titanium, trisdimethylaminocyclopentadienyl zirconium, etc., forming a film constituted by TiOC, ZrOC, etc.

In some embodiments, the first precursor is one or more compounds selected from the group consisting of:

wherein each X is independently H, C_(x)H_(y), NH₂, NH(C_(x)H_(y)), N(C_(x)H_(y))₂, O(C_(x)H_(y)), or OH, each Y is independently F, Cl, Br, I, NH₂, NH(C_(x)H_(y)), or N(C_(x)H_(y))₂, and each Z is independently C_(x)H_(y) or N_(x)H_(y), wherein x and y are integers.

In some embodiments, the second precursor is one or more compounds selected from the group consisting of:

wherein each X is independently C_(x)O_(y), O(C_(x)H_(y)), NH₂, NH(C_(x)H_(y)), N(C_(x)H_(y))₂, or OH, each Y is independently C_(x)H_(y) or N_(x)H_(y), each A is independently H or C_(x)H_(y), and each B is OH, C_(x)H_(y), O(C_(x)H_(y)), NH₂, NH(C_(x)H_(y)), N(C_(x)H_(y))₂, F, Cl, Br, or I, wherein x and y are integers.

In some embodiments, the first and second functional groups are an alkylamino group and a hydroxyl group, respectively, or a halogen group and a halogen group, respectively.

In some embodiments, a noble gas is continuously fed to the reaction space throughout the process cycle. In some embodiments, each process cycle further comprises a purging step between steps (i) and (ii), and between steps (ii) and (i) if the process cycle is repeated.

In some embodiments, the precursor is fed in a pulse to the reaction space using a flow-pass system (FPS), auto-pressure regulator (APR), or a bottle-out control system (BTO).

In some embodiments, the oxide or nitride film is a film constituted by SiC, SiCO, SiCN, or SiCON.

In some embodiments, the ALD is thermal ALD, and the substitution reaction is thermally performed.

In some embodiments, the ALD is plasma-enhanced ALD, and the substitution reaction is performed using a plasma. In some embodiments, a reactant gas is fed continuously to the reaction space throughout each process cycle. The reactant gas may be one or more gases selected from the group consisting of O₂, H₂, NH₃, and N₂.

In some embodiments, a sidewall coverage and a bottom coverage are 90% or higher, wherein the sidewall coverage is defined as a ratio of thickness of film on a sidewall of the trench to thickness of film on a blanket surface (a top surface of the substrate) at the trench, and the bottom coverage is defined as a ratio of thickness of film on a bottom of the trench to thickness of film on the blanket surface at the trench.

In some embodiments, in step (iii), the monolayer is constituted by SiC or SiCO, and each process cycle further comprises, after step (iii):

-   -   (iv) switching the reactant gas to another reactant gas and         feeding the another reactant continuously to the reaction space,     -   (v) feeding a third precursor in a pulse to the reaction space         to adsorb the third precursor on the substrate, said third         precursor containing at least one of silicon and metal and being         reactive with excited species of the another reactant; and     -   (vi) applying RF power to the reaction space to excite the         another reactant to react with the third precursor adsorbed on         the monolayer or monolayers obtained in step (iii) to form         thereon a monolayer or monolayers constituting a nitride film         containing at least one of silicon and metal.

By introducing Si—N bonds to a SiC/SiCO film, heat resistance and/or chemical resistance of the film can significantly be improved.

Some embodiments will be explained with respect to the drawings. However, the present invention is not limited to the embodiments.

FIG. 11 shows a schematic process sequence according to an embodiment of the present invention. In this sequence, an oxide or nitride film containing carbon and at least one of silicon and metal in a trench on a substrate placed in a reaction space is formed by atomic layer deposition (ALD) conducting one or more process cycles, each process cycle comprising: (i) feeding a first precursor in a pulse to the reaction space to adsorb the first precursor on the substrate, said first precursor containing at least one of silicon and metal, and a first functional group (step S11); (ii) feeding a second precursor in a pulse to the reaction space to adsorb the second precursor on the substrate, said second precursor containing neither silicon nor metal, and a second functional group (step S12); and (iii) forming a monolayer constituting an oxide or nitride film containing carbon and at least one of silicon and metal on the substrate by undergoing a substitution reaction between the first and second functional groups of the first and second precursors adsorbed on the substrate (step S13), wherein steps (i) to (iii) (steps S11, S12, and S13) are repeated until a desired thickness (e.g., 2 to 100 nm, typically 5 nm to 20 nm, depending on the intended use, etc.) of the film is obtained.

FIGS. 1 to 4 are schematic views of a plasma-enhanced ALD reactor and flow control systems, desirably in conjunction with controls programmed to conduct the sequences described below, which can be used in an embodiment of the present invention. A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) are communicated with the various power sources, heating systems, pumps, robotics, and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

In some embodiments, the process sequence may be set as illustrated in FIG. 6. FIG. 6 shows a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In this embodiment, one cycle of PEALD comprises “1^(st) Feed” where a first precursor gas (e.g., a Si-containing precursor gas) is fed to a reaction space via a carrier gas which carries the first precursor without feeding a second precursor and without applying RF power to the reaction space, and also, a dilution gas and a reactant gas are fed to the reaction space, thereby chemisorbing the first precursor gas onto a surface of a substrate via self-limiting adsorption; “Purge” where no first precursor nor second precursor is fed to the reaction space, while the carrier gas, the dilution gas, and reactant gas are continuously fed to the reaction space, without applying RF power, thereby removing non-chemisorbed precursor gas and excess gas from the surface of the substrate; “2^(nd) Feed” where a second precursor gas (e.g., a hydrocarbon-containing precursor gas) is fed to the reaction space via a carrier gas which carries the second precursor without feeding the first precursor and without applying RF power to the reaction space, and also, the dilution gas and the reactant gas are continuously fed to the reaction space, thereby chemisorbing the second precursor gas onto the first precursor-adsorbed surface of the substrate via self-limiting adsorption; “Purge” where no first precursor nor second precursor is fed to the reaction space, while the carrier gas, the dilution gas, and reactant gas are continuously fed to the reaction space, without applying RF power, thereby removing non-chemisorbed precursor gas and excess gas from the surface of the substrate; “RF” where RF power is applied to the reaction space while the carrier gas, the dilution gas, and reactant gas are continuously fed to the reaction space, without feeding the first and second precursors, thereby forming a monolayer through plasma surface reaction with the reactant gas in an excited state, wherein the ligand of the first precursor gas and the ligand of the second precursor gas undergo ligand substitution reaction to form a monolayer; and “Purge” where the carrier gas, the dilution gas, and reactant gas are continuously fed to the reaction space, without feeding the first and second precursors and without applying RF power to the reaction space, thereby removing by-products and excess gas from the surface of the substrate. The carrier gas can be constituted by the reactant gas. Due to the continuous flow of the carrier gas entering into the reaction space as a constant stream into which the first or second precursor is injected intermittently or in pulses, purging can be conducted efficiently to remove excess gas and by-products quickly from the surface of the layer, thereby efficiently continuing multiple ALD cycles.

The sequence illustrated in FIG. 6 can be performed under the conditions shown in Table 2 below.

TABLE 2 (numbers are approximate) Conditions for PEALD Cycle (Sequence #2) Substrate temperature 50 to 600° C. (preferably 100 to 400° C.) Pressure 50 to 4000 Pa (preferably 133 to 1000 Pa) 1^(st) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 1^(st) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) 2^(nd) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 2^(nd) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) Flow rate of reactant 10 to 2000 sccm (preferably 50 to 500 sccm) (continuous) for SiC; 10 to 2000 sccm (preferably 50 to 500 sccm) for SiCO; 10 to 2000 sccm (preferably 50 to 500 sccm) for SiCN Carrier gas 1000 to 5000 sccm (preferably 2000 to 4000 sccm) Dilution gas 0 to 5000 sccm (preferably 0 to 2000 sccm) RF power (13.56 MHz) 30 to 1000 W (preferably 50 to 200 W) for a 300-mm wafer RF power pulse 0.1 to 10 sec (preferably 0.2 to 5 sec) Purge 0.1 to 5 sec (preferably 0.1 to 1 sec) Growth rate per cycle 0.01 to 0.1 nm/cycle (on a top surface)

In this disclosure, the wattage of RF power for a 300-mm wafer can be expressed using units W/cm² which can be applied to a different size of substrate such as a 200-mm substrate and a 450-mm substrate; likewise, “W” can be converted to “W/cm²” in this disclosure. Further, in place of direct plasma, remote plasma can be used to form active species of reactant in the reaction space.

In the above process sequence, the precursor is supplied in a pulse using a carrier gas which is continuously supplied. This can be accomplished using a flow-pass system (FPS) wherein a carrier gas line is provided with a detour line having a precursor reservoir (bottle), and the main line and the detour line are switched, wherein when only a carrier gas is intended to be fed to a reaction chamber, the detour line is closed, whereas when both the carrier gas and a precursor gas are intended to be fed to the reaction chamber, the main line is closed and the carrier gas flows through the detour line and flows out from the bottle together with the precursor gas. In this way, the carrier gas can continuously flow into the reaction chamber, and can carry the precursor gas in pulses by switching the main line and the detour line. FIG. 1B illustrates a precursor supply system using a flow-pass system (FPS) according to an embodiment of the present invention (black valves indicate that the valves are closed). As shown in (a) in FIG. 1B, when feeding a precursor to a reaction chamber (not shown), first, a carrier gas such as Ar (or He) flows through a gas line with valves b and c, and then enters a bottle (reservoir) 20. The carrier gas flows out from the bottle 20 while carrying a precursor gas in an amount corresponding to a vapor pressure inside the bottle 20, and flows through a gas line with valves f and e, and is then fed to the reaction chamber together with the precursor. In the above, valves a and d are closed. When feeding only the carrier gas (noble gas) to the reaction chamber, as shown in (b) in FIG. 1B, the carrier gas flows through the gas line with the valve a while bypassing the bottle 20. In the above, valves b, c, d, e, and f are closed.

The precursor may be provided with the aid of a carrier gas. Since ALD is a self-limiting adsorption reaction process, the number of deposited precursor molecules is determined by the number of reactive surface sites and is independent of precursor exposure after saturation, and a supply of the precursor is such that the reactive surface sites are saturated thereby per cycle. A plasma for deposition may be generated in situ, for example, in an ammonia gas that flows continuously throughout the deposition cycle. In other embodiments the plasma may be generated remotely and provided to the reaction chamber.

As mentioned above, each pulse or phase of each deposition cycle is preferably self-limiting. An excess of reactants is supplied in each phase to saturate the susceptible structure surfaces. Surface saturation ensures reactant occupation of all available reactive sites (subject, for example, to physical size or “steric hindrance” restraints) and thus ensures excellent step coverage. In some embodiments the pulse time of one or more of the reactants can be reduced such that complete saturation is not achieved and less than a monolayer is adsorbed on the substrate surface.

The process cycle can be performed using any suitable apparatus including an apparatus illustrated in FIG. 1A, for example. FIG. 1A is a schematic view of a PEALD apparatus, desirably in conjunction with controls programmed to conduct the sequences described below, usable in some embodiments of the present invention. In this figure, by providing a pair of electrically conductive flat-plate electrodes 4, 2 in parallel and facing each other in the interior 11 (reaction zone) of a reaction chamber 3, applying HRF power (13.56 MHz or 27 MHz) 20 to one side, and electrically grounding the other side 12, a plasma is excited between the electrodes. A temperature regulator is provided in a lower stage 2 (the lower electrode), and a temperature of a substrate 1 placed thereon is kept constant at a given temperature. The upper electrode 4 serves as a shower plate as well, and reactant gas (and noble gas) and precursor gas are introduced into the reaction chamber 3 through a gas line 21 and a gas line 22, respectively, and through the shower plate 4. Additionally, in the reaction chamber 3, a circular duct 13 with an exhaust line 7 is provided, through which gas in the interior 11 of the reaction chamber 3 is exhausted. Additionally, a dilution gas is introduced into the reaction chamber 3 through a gas line 23. Further, a transfer chamber 5 disposed below the reaction chamber 3 is provided with a seal gas line 24 to introduce seal gas into the interior 11 of the reaction chamber 3 via the interior 16 (transfer zone) of the transfer chamber 5 wherein a separation plate 14 for separating the reaction zone and the transfer zone is provided (a gate valve through which a wafer is transferred into or from the transfer chamber 5 is omitted from this figure). The transfer chamber is also provided with an exhaust line 6. In some embodiments, the deposition of multi-element film and surface treatment are performed in the same reaction space, so that all the steps can continuously be conducted without exposing the substrate to air or other oxygen-containing atmosphere. In some embodiments, a remote plasma unit can be used for exciting a gas.

In some embodiments, in the apparatus depicted in FIG. 1A, the system of switching flow of an inactive gas and flow of a precursor gas illustrated in FIG. 1B (described earlier) can be used to introduce the precursor gas in pulses without substantially fluctuating pressure of the reaction chamber.

The precursor can be fed in a pulse to the reaction space not only using a flow-pass system (FPS), but also auto-pressure regulator (APR), a bottle-out control system (BTO), or mass flow controller (MFC). FIG. 2 illustrates a precursor supply system using an auto-pressure regulator (APR) according to an embodiment of the present invention. As shown in (a) in FIG. 2, when feeding a precursor to a reaction chamber (not shown), first, a carrier gas flows through a gas line with valves b and c, and then enters a bottle 20. The carrier gas flows out from the bottle 20 while carrying a precursor gas in an amount corresponding to a vapor pressure inside the bottle 20, and flows through a gas line with valves f and e, and is then fed to the reaction chamber together with the precursor through an auto-pressure regulator (APR) 30 and a valve g provided in a gas line upstream of the reaction chamber. In the above, valves a and d are closed. Valve g is an on-off valve, and when preventing the precursor from entering into the reaction chamber, as shown in (b) in FIG. 2, valve g is closed so that neither the precursor nor the carrier gas is fed to the reaction chamber.

FIG. 3 illustrates a precursor supply system using a bottle-out control system (BTO) according to an embodiment of the present invention. As shown in (a) in FIG. 3, when a carrier gas flows through a gas line with a valve a to a reaction chamber (not shown) without passing through a bottle 20, a precursor gas enters into a stream of the carrier gas passing through the gas line where a gas line from the bottle 20 meets the gas line through which the carrier gas flows, and the carrier gas carries the precursor therefrom and is then fed to the reaction chamber together with the precursor. In the above, valves b and c are closed, and valves e and f are open so that when the vapor pressure inside the bottle 20 is higher than the pressure of the carrier gas passing through the gas line, the precursor flows from the bottle 20 and enters into the stream of the carrier gas. When feeding only the carrier gas to the reaction chamber, as shown in (b) in FIG. 3, the carrier gas flows through a gas line and passes through valve a while bypassing the bottle 20. In the above, valves b, c, e, and f are closed.

FIG. 4 illustrates a precursor supply system using an APR with a BTO according to an embodiment of the present invention. As shown in (a) in FIG. 4, when a carrier gas flows through a gas line with a valve a to a reaction chamber (not shown) without passing through a bottle 20, a precursor gas enters into a stream of the carrier gas passing through the gas line where a gas line from the bottle 20 meets the gas line through which the carrier gas flows, and the carrier gas carries the precursor therefrom and passes through an APR 30 and a valve g together with the precursor, and is then fed to the reaction chamber together with the precursor. In the above, valves b and c are closed, and valves e and f are open so that when the vapor pressure inside the bottle 20 is higher than the pressure of the carrier gas passing through the gas line, the precursor flows from the bottle 20 and enters into the stream of the carrier gas. Valve g is an on-off valve, and when preventing the precursor from entering into the reaction chamber, as shown in (b) in FIG. 4, valve g is closed so that neither the precursor nor the carrier gas is fed to the reaction chamber.

In some embodiments, the process sequence may be set as illustrated in FIG. 7. FIG. 7 shows a schematic process sequence of PEALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In this embodiment, a primary difference from the sequence illustrated in FIG. 6 resides in “RF” which is conducted after purging the first precursor gas, followed by “Purge” before feeding the second precursor gas, so that adsorption of the first precursor can be improved.

The sequence illustrated in FIG. 6 can be performed under the conditions shown in Table 3 below.

TABLE 3 (numbers are approximate) Conditions for PEALD Cycle (Sequence #3) Substrate temperature 50 to 600° C. (preferably 100 to 400° C.) Pressure 50 to 4000 Pa (preferably 133 to 1000 Pa) 1^(st) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 1^(st) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) RF power (13.56 MHz) 30 to 1000 W (preferably 50 to 200 W) for a 300-mm wafer RF power pulse 0.1 to 10 sec (preferably 0.2 to 5 sec) Purge 0.1 to 5 sec (preferably 0.1 to 1 sec) 2^(nd) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 2^(nd) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) RF power (13.56 MHz) 30 to 1000 W (preferably 50 to 200 W) for a 300-mm wafer RF power pulse 0.1 to 10 sec (preferably 0.2 to 5 sec) Purge 0.1 to 5 sec (preferably 0.1 to 1 sec) Flow rate of reactant 10 to 2000 sccm (preferably 50 to 500 sccm) (continuous) for SiC; 10 to 2000 sccm (preferably 50 to 500 sccm) for SiCO; 10 to 2000 sccm (preferably 50 to 500 sccm) for SiCN Carrier gas 1000 to 5000 sccm (preferably 2000 to 4000 sccm) Dilution gas 0 to 5000 sccm (preferably 0 to 2000 sccm) Growth rate per cycle 0.01 to 0.1 nm/cycle (on a top surface)

In some embodiments, the process sequence may be set as illustrated in FIG. 8. FIG. 8 shows a schematic process sequence of thermal ALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In this embodiment, one cycle of PEALD comprises “1^(st) Feed” where a first precursor gas (e.g., a Si-containing precursor gas) is fed to a reaction space via a carrier gas which carries the first precursor without feeding a second precursor to the reaction space, and also, a dilution gas is fed to the reaction space, thereby adsorbing the first precursor gas onto a surface of a substrate via self-limiting adsorption; “Purge” where no first precursor nor second precursor is fed to the reaction space, while the carrier gas and the dilution gas are continuously fed to the reaction space, thereby removing non-adsorbed precursor gas and excess gas from the surface of the substrate; “2^(nd) Feed” where a second precursor gas (e.g., a hydrocarbon-containing precursor gas) is fed to the reaction space via a carrier gas which carries the second precursor without feeding the first precursor to the reaction space, and also, the dilution gas is continuously fed to the reaction space, thereby adsorbing the second precursor gas onto the first precursor-adsorbed surface of the substrate via self-limiting adsorption, wherein the ligand of the first precursor gas and the ligand of the second precursor gas undergo ligand substitution reaction; and “Purge” where the carrier gas and the dilution gas are continuously fed to the reaction space, without feeding the first and second precursors to the reaction space, thereby removing by-products and excess gas from the surface of the substrate. Due to the continuous flow of the carrier gas entering into the reaction space as a constant stream into which the first or second precursor is injected intermittently or in pulses, purging can be conducted efficiently to remove excess gas and by-products quickly from the surface of the layer, thereby efficiently continuing multiple ALD cycles.

In the sequence illustrated in FIG. 8, no reactant gas is used since the first and second precursors can undergo ligand substitution reaction without a reactant gas. The “adsorption” is more likely “polymerization”. This sequence is precursor-dependent because reactivity of the precursors depends on the types of the ligands contained in the first and second precursors. For example, when the ligand is a hydroxyl group, after being adsorbed on the other precursor, some components are dissociated from the surface, and the components generate moisture which causes hydrolysis, thereby forming a bulk film.

The sequence illustrated in FIG. 8 can be performed under the conditions shown in Table 4 below.

TABLE 4 (numbers are approximate) Conditions for Thermal ALD Cycle (Sequence #4) Substrate temperature 50 to 600° C. (preferably 100 to 400° C.) Pressure 50 to 4000 Pa (preferably 133 to 1000 Pa) 1^(st) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 1^(st) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) 2^(nd) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 2^(nd) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) Carrier gas 1000 to 5000 sccm (preferably 2000 to 4000 sccm) Dilution gas 1000 to 5000 sccm (preferably 500 to 2000 sccm) Growth rate per cycle 0.01 to 0.1 nm/cycle (on a top surface)

In some embodiments, the process sequence may be set as illustrated in FIG. 9. FIG. 9 shows a schematic process sequence of thermal ALD in one cycle according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In this embodiment, a primary difference from the sequence illustrated in FIG. 8 resides in “Reactant” which is conducted after purging the second precursor gas, followed by “Thermal” wherein a reactant gas is fed in “Reactant” and causes ligand substitution reaction in “Thermal” wherein the ligand of the first precursor gas and the ligand of the second precursor gas undergo ligand substitution reaction to form a monolayer. “Reactant” is a period mainly for stabilizing the reactant flow, and “Thermal” is a period mainly for ligand substitution reaction (in some embodiments, “Reactant” and “Thermal” are continuous integrated steps constituting a single step of thermal ligand substitution reaction). After “Thermal”, “Purge” is conducted where the carrier gas and the dilution gas are continuously fed to the reaction space, without feeding the first and second precursors and the reactant gas to the reaction space, thereby removing by-products and excess gas from the surface of the substrate. This sequence can improve adsorption of the first and second precursors and promote ligand substitution reaction.

The sequence illustrated in FIG. 9 can be performed under the conditions shown in Table 5 below.

TABLE 5 (numbers are approximate) Conditions for Thermal ALD Cycle (Sequence #5) Substrate temperature 50 to 600° C. (preferably 100 to 400° C.) Pressure 50 to 4000 Pa (preferably 133 to 1000 Pa) 1^(st) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 1^(st) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) 2^(nd) precursor pulse 0.1 to 2 sec (preferably 0.3 to 1 sec) 2^(nd) precursor purge 0.1 to 10 sec (preferably 0.5 to 1 sec) Flow rate of reactant 10 to 2000 sccm (preferably 50 to 500 sccm) for SiC; 10 to 2000 sccm (preferably 50 to 500 sccm) for SiCO; 10 to 2000 sccm (preferably 50 to 500 sccm) for SiCN Reactant introduction 0.2 to 10 sec (preferably 1 to 5 sec) Thermal Reaction duration 0.5to 60 sec (preferably 1 to 30 sec) Post reaction purge 0.1 to 2 sec (preferably 0.1 to 1 sec) Carrier gas 1000 to 5000 sccm (preferably 2000 to 4000 sccm) Dilution gas 0 to 5000 sccm (preferably 0 to 2000 sccm) Growth rate per cycle 0.01 to 0.1 nm/cycle (on a top surface)

In some embodiments, the process sequence may be set as illustrated in FIG. 10. FIG. 10 shows a schematic process sequence of PEALD in one cycle, followed by the schematic process sequence of PEALD illustrated in FIG. 6 or 7 according to an embodiment of the present invention wherein a cell in gray represents an ON state whereas a cell in white represents an OFF state, and the width of each column does not represent duration of each process. In this embodiment, a SiC or SiCO film is formed according to the sequence illustrated in FIG. 6 or 7, and thereafter, a SiN film is formed, thereby alternately forming a SiC/SiCO film and a SiN film so as to form a SiCN or SiCON film, increasing heat resistance and/or chemical resistance. By incorporating Si—N bonds into the SiC/SiCO film, heat resistance/chemical resistance of the film can be improved. In this sequence, after the “Purge” following “2^(nd) Feed” in FIG. 6 or 7, a SiN cycle starts, wherein one cycle of PEALD comprises “Transit” where flow of the reactant gas (1^(st) reactant) used in the sequence illustrated in FIG. 6 or 7 is stopped, while continuously feeding the carrier gas and the dilution gas to the reaction space, thereby purging the reaction space; “3^(rd) Feed” where a third precursor gas (e.g., a Si-containing precursor gas) for forming a SiN film is fed to the reaction space via a carrier gas which carries the first precursor without feeding the first and second precursors and the 1^(st) reactant gas and without applying RF power to the reaction space, and also, the dilution gas is continuously fed, and a 2^(nd) reactant gas is fed to the reaction space for forming a SiN film, thereby chemisorbing the third precursor gas onto the surface of the substrate via self-limiting adsorption; “Purge” where none of the first, second, and third precursors and the 1^(st) reactant gas is fed to the reaction space, while the carrier gas, the dilution gas, and 2^(nd) reactant gas are continuously fed to the reaction space, without applying RF power, thereby removing non-chemisorbed precursor gas and excess gas from the surface of the substrate; “RF” where RF power is applied to the reaction space while the carrier gas, the dilution gas, and 2^(nd) reactant gas are continuously fed to the reaction space, without feeding the first, second, and third precursors and the 1^(st) reactant gas, thereby forming a SiN monolayer through plasma surface reaction with the 2^(nd) reactant gas in an excited state; and “Purge” where the carrier gas, the dilution gas, and 2^(nd) reactant gas are continuously fed to the reaction space, without feeding the first, second, and third precursors and the 1^(st) reactant gas and without applying RF power to the reaction space, thereby removing by-products and excess gas from the surface of the substrate.

In this sequence, in some embodiments, the cycle for forming a SiC/SiCO film illustrated in FIG. 6 or 7 can be repeated m times, the cycle for forming a SiN film illustrated in FIG. 10 can be repeated n times, and the cycle combining the cycle for a SiC/SiCO film and the cycle for a SiN film can be repeated p times, wherein m is an integer of 10 to 5000, preferably 50 to 2000, n is an integer of 10 to 5000, preferably 50 to 2000, and p is an integer of 10 to 5000, preferably 50 to 2000.

The sequence illustrated in FIG. 10 can be performed under the conditions shown in Table 6 below.

TABLE 6 (numbers are approximate) Conditions for PEALD Cycle (Sequence #6) Substrate temperature Same as Sequence #2 or #3 Pressure Same as Sequence #2 or #3 3^(rd) precursor pulse 0.1 to 5 sec (preferably 0.1 to 1 sec) 3^(rd) precursor purge 0.1 to 5 sec (preferably 1 to 5 sec) Flow rate of 2^(nd) reactant 100 to 10000 sccm (preferably 1000 to (continuous) 5000 sccm) Carrier gas Same as Sequence #2 or #3 Dilution gas Same as Sequence #2 or #3 RF power (13.56 MHz) 50 to 1000 W (preferably 100 to 500 W) for a 300-mm wafer RF power pulse 0.2 to 10 sec (preferably 0.5 to 5 sec) Purge 0.1 to 2 sec (preferably 0.1 to 0.5 sec) Growth rate per cycle 0.01 to 0.08 nm/cycle (on a top surface)

In the above sequence, the third precursor includes, but is not limited to, a halogen-containing silane such as dichlorotetramethyldisilane, diiodosilane, etc. In some embodiments, the third precursor may be selected from the first precursors. The second reactant gas includes, but is not limited to, N₂, N₂/H₂, NH₃, NxHy (x>2; y>3), NxCyHz (x, y, z are integers), etc.

In some embodiments, a dual-chamber reactor (two sections or compartments for processing wafers disposed close to each other) can be used, wherein a reactant gas and a noble gas can be supplied through a shared line whereas a precursor gas is supplied through unshared lines.

A skilled artisan will appreciate that the apparatus includes one or more controller(s) (not shown) programmed or otherwise configured to cause the deposition and reactor cleaning processes described elsewhere herein to be conducted. The controller(s) are communicated with the various power sources, heating systems, pumps, robotics, and gas flow controllers or valves of the reactor, as will be appreciated by the skilled artisan.

The present invention is further explained with reference to working examples below. However, the examples are not intended to limit the present invention. In the examples where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation. Also, the numbers applied in the specific examples can be modified by a range of at least ±50% in some embodiments, and the numbers are approximate.

EXAMPLES

A SiC or SiCO film was formed on a Si substrate (Φ300 mm) having trenches with an aspect ratio (AR) of 2 or 3.5 (a width of 35 nm) by thermal ALD using a sequence illustrated in FIG. 8 (SQ #4) or FIG. 9 (SQ #5), and also by PEALD using a sequence illustrated in FIG. 5 (SQ #1), FIG. 6 (SQ #2), or FIG. 7 (SQ #3), one cycle of which was conducted under the common conditions for all the sequences shown in Table 7, the common conditions for the sequences illustrated in FIGS. 5-9 shown in Tables 8-12 below, respectively. For PEALD, the PEALD apparatus illustrated in FIG. 1A and a gas supply system (FPS) illustrated in FIG. 2 were used. The specific conditions for each example are indicated in Table 13.

TABLE 7 (numbers are approximate) Common Conditions for Deposition Cycle Substrate temperature 400° C. Pressure 400 Pa Carrier gas Ar Flow rate of carrier gas (continuous) 2000 sccm

TABLE 8 (numbers are approximate) Conditions for PEALD Cycle (Sequence #1 (FIG. 5)) Precursor pulse 0.1 Sec Precursor purge 1 Sec RF power (13.56 MHz) for a 100 W 300-mm wafer RF power pulse 1 sec Purge 0.1 sec Dilution gas Ar: 100 Sccm

TABLE 9 (numbers are approximate) Conditions for PEALD Cycle (Sequence #2 (FIG. 6)) Si-precursor pulse 0.5 sec Si-precursor purge 0.5 sec C-precursor pulse 1 sec C-precursor purge 1 sec Flow rate of reactant H2; 100 sccm for SiC; (continuous) O2; 100 sccm for SiCO Dilution gas Ar: 100 sccm RF power (13.56 MHz) for a 100 W 300-mm wafer RF power pulse 1 sec Purge 0.1 sec

TABLE 10 (numbers are approximate) Conditions for PEALD Cycle (Sequence #3 (FIG. 7)) Si-precursor pulse 0.5 sec Si-precursor purge 0.5 sec RF power (13.56 MHz) for a 100 W 300-mm wafer RF power pulse 1 sec Purge 0.1 sec C-precursor pulse 1 sec C-precursor purge 1 sec RF power (13.56 MHz) for a 100 W 300-mm wafer RF power pulse 1 sec Purge 0.1 sec Flow rate of reactant H2; 100 sccm for SiC (continuous) Dilution gas Ar: 100 sccm

TABLE 11 (numbers are approximate) Conditions for Thermal ALD Cycle (Sequence #4 (FIG. 8)) Si-precursor pulse 0.5 Sec Si-precursor purge 0.5 Sec C-precursor pulse 1 Sec C-precursor purge 1 Sec Dilution gas Ar: 500 sccm

TABLE 12 (numbers are approximate) Conditions for Thermal ALD Cycle (Sequence #5 (FIG. 9)) Si-precursor pulse 0.5 Sec Si-precursor purge 0.5 Sec C-precursor pulse 1 sec C-precursor purge 1 sec Flow rate of reactant 100 sccm Reactant pulse 1 sec Thermal Reaction pulse 5 sec Post reaction purge 1 sec Dilution gas Ar: 100 sccm

TABLE 13 (numbers are approximate) Reactant RF 1^(st) Precursor 2^(nd) Precursor (flow rate) [W] SQ Film *1 Divinyldimethylsilane — O₂ 100 1 SiCO (0.1 slm) *2 Silacyclobutane — H₂ 100 1 SiC (0.1 slm)  3 Bisdiethylaminosilane Ethyleneglycol O₂ 100 2 SiCO (0.1 slm)  4 Bisdiethylaminosilane Ethyleneglycol — 4 SiCO  5 Diiodosilane Iodomethane H₂ 100 2 SiC (0.1 slm)  6 Diiodosilane Iodomethane — — 4 SiC  7 Diiodosilane Diiodomethane H₂ 100 2 SiC (0.1 slm)  8 Diiodosilane Diiodomethane H₂ 100 3 SiC (0.1 slm)  9 Diiodosilane Diiodomethane H₂ — 5 SiC (0.1 slm)

In Table 13, the Example numbers with “*” indicate comparative examples. Each obtained film was evaluated, and “Film” represents compositions of the film, and “SQ” represents the sequence number where SQ #1 to SQ #5 correspond to the sequences illustrated in FIGS. 5 to 9, respectively. Table 10 shows the results of evaluation.

TABLE 14 (the numbers are approximate) AR 2 AR 3.5 Bottom Bottom Sidewall coverage Sidewall coverage GPC coverage (bottom/ coverage (bottom/ (nm/ RI@ (side/top) top) (side/top) top) cycle) 633 nm (%) (%) (%) (%) *1 0.03 1.6 90 92 70 90 *2 0.03 1.64 90 95 75 90  3 0.04 1.69 95 93 92 95  4 0.02 1.67 96 95 9 95  5 0.04 1.7 93 95 93 93  6 0.02 1.65 97 93 92 92  7 0.06 1.68 97 94 93 96  8 0.06 1.69 94 92 91 96  9 0.03 1.7 94 96 97 92

In Table 14, “GPC” represents growth rate per cycle, “Sidewall Coverage” represents a percentage of thickness of film deposited on a sidewall relative to thickness of film deposited on a blanket surface (a top surface of the substrate) at a trench having a specified aspect ratio (2 or 3.5), “Bottom Coverage” represents a percentage of thickness of film deposited on a bottom surface relative to thickness of film deposited on a blanket surface at a trench having a specified aspect ratio (2 or 3.5), and “RI@633 nm,” represents refractive index at a wavelength of 633 nm.

In the above examples, a SiC film was formed using diiodosilane as a first precursor and iodomethane or diiodomethane as a second precursor in thermal ALD (Example 6) and PEALD (Examples 5 and 7 to 9), and a SiCO film was formed using bisdiethyaminosilane as a first precursor and ethyleneglycol as a second precursor in thermal ALD (Example 4) and PEALD (Example 3). As comparative examples, a SiC film was formed using divinyldimethylsilane as a single precursor in PEALD (Example 2), and a SiCO film was formed using divinyldimethylsilane as a single precursor in PEALD (Example 1). As a result, in all the examples, effective reaction took place for both SiC film and SiCO film in thermal ALD at a temperature of 400° C., and also in PEALD. However, when the single precursor was used in Examples 1 and 2, overall step coverage was inferior to that when the two precursors were used in Examples 3 to 9, and especially when the aspect ratio was 3.5, the sidewall coverage was poor when the single precursor was used in Examples 1 and 2, as compared with that when the two precursors were used in Examples 3 to 9 which showed remarkable improvements on the step coverage. It was confirmed that a carbon-containing film can successfully be formed with good conformality (e.g., more than 90%) even on sidewalls of a trench having an aspect ratio of more than 2 by using 1^(st) and 2^(nd) precursors in combination, wherein the 1^(st) precursor contains silicon and at least one 1^(st) ligand, and the 2^(nd) precursor contains no silicon and at least one 2^(nd) ligand, where the 1^(st) ligand and the 2^(nd) ligand can undergo ligand substitution reaction.

The above remarkable results can be obtained when the 1^(st) precursor contains a metal instead of silicon (or in combination), since ligand substitution reaction can similarly take place. In addition, the feeding order of the 1^(st) precursor and 2^(nd) precursor can be reversed.

It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention. 

We claim:
 1. A method for forming a target film, other than a nitride film, containing carbon, oxygen, and silicon in a trench on a substrate placed in a reaction space by a process of atomic layer deposition (ALD) continuously repeating a deposition cycle throughout the process of ALD until the target film is formed, each deposition cycle forming a monolayer comprising steps of: (i) feeding a first precursor in a first pulse to the reaction space to adsorb the first precursor on the substrate, said first precursor containing silicon, and a first functional group selected from the group consisting of a first halogen group, and —NR¹ ₂, wherein each R¹ independently represents hydrogen or hydrocarbon group; (ii) feeding a second precursor in a second pulse to the reaction space to adsorb the second precursor on the substrate, said second precursor having no —NR² ₂ and containing carbon but neither silicon nor metal, and a second functional group which is —OR², wherein each R² independently represents hydrogen or hydrocarbon group, wherein the first and second functional groups are a combination of the first halogen group and the —OR², or the —NR¹ ₂ and the —OR², wherein each deposition cycle further comprising a purging step immediately following step (i), said purging step being immediately followed by step (ii), wherein (1) the first precursor is stored in liquid form in a first bottle, and is fed in the first pulse to the reaction space using a first flow-pass system (FPS) or a first bottle-out control system (BTO), wherein (1a) the first BTO is operated in a manner that a gas phase of the first precursor, while flowing from the first bottle, is merged into a flow of carrier gas upstream of the reaction space only when a vapor pressure of the first precursor inside the first bottle is higher than a pressure of the flow of carrier gas where the first precursor is merged into the flow of carrier gas wherein the carrier gas carries the gas phase of the first precursor without entering the first bottle throughout the step (i), or (1b) the first FPS is operated in a manner that the carrier gas flows continuously throughout the step (i) wherein the carrier gas carries the gas phase of the first precursor by passing through the first bottle, whereas being redirected to bypass the first bottle when not carrying the gas phase of the first precursor; and also (2) the second precursor is stored in liquid form in a second bottle, and is fed in the second pulse to the reaction space using a second flow-pass system (FPS) or a second bottle-out control system (BTO), wherein (2a) the second BTO is operated in a manner that a gas phase of the second precursor, while flowing from the second bottle, is merged into a flow of carrier gas upstream of the reaction space only when a vapor pressure of the second precursor inside the second bottle is higher than a pressure of the flow of carrier gas where the second precursor is merged into the flow of carrier gas wherein the carrier gas carries the gas phase of the second precursor without entering the second bottle throughout the step (ii), or (2b) the second FPS is operated in a manner that the carrier gas flows continuously throughout the step (ii) wherein the carrier gas carries the gas phase of the second precursor by passing through the second bottle, whereas being redirected to bypass the second bottle when not carrying the gas phase of the second precursor, wherein the first precursor together with the carrier gas is fed in the first pulse created by a first pulsing valve to the reaction space via a first auto pressure regulator (APR) without using a mass flow controller (MFC) wherein the first APR is provided upstream of the first pulsing valve, and the second precursor together with the carrier gas is fed in the second pulse created by a second pulsing valve to the reaction space via a second auto pressure regulator (APR) without using a mass flow controller (MFC) wherein the second auto pressure regulator is provided upstream of the second pulsing valve, and (iii) forming a monolayer constituting a portion of the target film containing carbon, oxygen, and silicon on the substrate by undergoing a substitution reaction between the first and second functional groups of the first and second precursors adsorbed on the substrate, wherein as a result of repeating the steps (i) to (iii), each said monolayer accumulates thereby constituting the target film.
 2. The method according to claim 1, wherein the first precursor is one or more compounds selected from the group consisting of:

wherein each X is independently H, C_(x)H_(y), NH₂, NH(C_(x)H_(y)), N(C_(x)H_(y))₂, O(C_(x)H_(y)), or OH, and each Y is independently F, Cl, Br, I, NH₂, NH(C_(x)H_(y)), or N(C_(x)H_(y))₂, wherein x and y are integers of more than 0 which form chemically possible valence structures of the first precursor.
 3. The method according to claim 1, wherein the second precursor is one or more compounds selected from the group consisting of:

wherein each X is independently O(C_(x)H_(y)) or OH, each Y is independently C_(x)H_(y), each A is independently H or C_(x)H_(y), and each B is OH or O(C_(x)H_(y)), wherein x and y are integers of more than 0 which form chemically possible valence structures of the second precursor.
 4. The method according to claim 1, wherein the first and second functional groups are an alkylamino group and a hydroxyl group, respectively.
 5. The method according to claim 1, wherein a noble gas is continuously fed to the reaction space throughout the deposition cycle.
 6. The method according to claim 1, wherein the target film is a film constituted by SiCO which is an abbreviation indicating a film type in a non-stoichiometric manner.
 7. The method according to claim 1, wherein the ALD is thermal ALD, and the substitution reaction is thermally performed.
 8. The method according to claim 1, wherein the ALD is plasma-enhanced ALD, and the substitution reaction is performed using a plasma.
 9. The method according to claim 8, wherein a reactant gas is fed continuously to the reaction space throughout each deposition cycle, wherein in the step (iii), the substitution reaction comprises applying RF power to the reaction space to excite the reactant gas.
 10. The method according to claim 9, wherein the reactant gas is one or more gases selected from the group consisting of O₂ and H₂.
 11. The method according to claim 1, wherein a sidewall coverage and a bottom coverage are 90% or higher, wherein the sidewall coverage is defined as a ratio of thickness of a portion of the target film on a sidewall of the trench to thickness of a portion of the target film on a blanket surface at the trench, and the bottom coverage is defined as a ratio of thickness of a portion of the target film on a bottom of the trench to thickness of the portion of the target film on the blanket surface at the trench.
 12. The method according to claim 1, wherein the first precursor is fed in the first pulse to the reaction space using the first BTO with the first auto pressure regulator (APR) which is provided downstream of a point where the gas phase of the first precursor is merged into the flow of carrier gas, and the second precursor is fed in the second pulse to the reaction space using the second BTO with the second auto pressure regulator (APR) which is provided downstream of a point where the gas phase of the second precursor is merged into the flow of carrier gas.
 13. The method according to claim 1, wherein the first precursor is fed in the first pulse to the reaction space using the first FPS, and the second precursor is fed in the second pulse to the reaction space using the second FPS. 